1. Field of the Invention
The invention relates to a steering device.
2. Description of Related Art
For example, in a steering column for an automobile described in Published Japanese Translation of PCT application No, 2011-516323 (JP 2011-516323 A), a steering shaft to which a steering wheel is mounted is rotatably supported by an adjustment unit supported by a support unit. When the adjustment unit is moved in an axial direction of the steering shaft, it is possible to adjust the position of the steering wheel in the axial direction.
The adjustment unit is disposed between a pair of side plates in the support unit. Each side plate is provided with a hole, and a clamping bolt is inserted into the hole. A lock member is attached to the clamping bolt, and an operation lever is coupled to the clamping bolt. To the adjustment unit, an opposite lock member formed with a large number of notches is coupled via a breakaway plate.
When the operation lever is operated and the clamping bolt is thereby rotated, a protrusion of the lock member is inserted into any of the notches of the opposite lock member, and the position of the steering wheel in the axial direction is locked. At the time of vehicle collision, due to the breakage of the breakaway plate, energy exerted at the time of vehicle collision is absorbed.
In the steering column described in JP-A-2011-516323, a half-locked state in which the protrusion of the lock member is not inserted into the notch but is kept in pressure contact with a boundary portion between the adjacent notches in the opposite lock member can occur. When the vehicle collision occurs in the half-locked state, depending on a collision speed, it takes time for the protrusion to be engaged with the near notch before the breakaway plate is broken (before separation) so that the timing of breakage of the breakaway plate is delayed. As a result, there is a possibility that variations occur in characteristics of energy absorption (what is called separation characteristics) at the time of the vehicle collision in accordance with a distance of movement of the protrusion before the protrusion is engaged with the notch.